1. Field of the Invention
The present invention relates to a roll for a mill in which the strength of bonding between a ring and a roll shaft is highly enhanced.
2. Prior Art
FIGS. 1 to 4 of the accompanying drawings show rolls for a mill hitherto used. One conventional roll shown in FIG. 1, generally designated at A, comprises a roll shaft 100 having a tapered portion 100a disposed intermediate opposite ends thereof, a ring 102 of a wear-resistant material disposed around the tapered portion 100a, and a tapered tubular sleeve 104 press-fitted between the tapered portion 100a and the ring 102. In this roll, the ring 102 is first disposed around the tapered portion 100a, and the tapered sleeve 104 is then forced in between the ring 102 and the tapered portion 100a by means of a press member 106, so that the sleeve 104 as well as the ring 102 can be rigidly retained in place owing to frictional forces caused between the contact surfaces.
Another conventional roll B shown in FIG. 2 comprises a roll shaft 108 having a tapered portion 108a and an internal fluid passageway 110 so formed as to be located adjacent the outer peripheral surface of the tapered portion 108a. A pair of collars 112 and 112 and a ring 114 are fitted on the tapered portion 108a and fixedly secured thereto by a nut 116 threaded onto the shaft 108. In this roll, the passageway 110 is supplied with oil, and the tapered portion 108a is enlarged in diameter owing to pressure of the oil contained in the passageway 110. Hence, the collars 112 and the ring 114 are tightly secured to the shaft 108 not only owing to a fastening force caused by the nut 116 but also owing to the enlargement of the tapered portion 108a.
A further conventional roll C shown in FIG. 3 is similar to the roll A in that it comprises a roll shaft 118 having a tapered portion 118a, a ring 120 disposed around the tapered portion 118a, and a tapered tubular sleeve 122 pressfitted between the tapered portion 118a and the ring 120. The roll, however, includes a radially extending bore 124 formed through the shaft 118, a screw member 126 threaded through the shaft 118 so that its forward end protrudes into the bore 124, and a key member 128 passing through the sleeve 122 and received in the bore 124. In this roll, the ring 120 is first disposed around the shaft 118, and the sleeve 122 is then forced in between the ring 120 and the shaft 118 by means of a pressing apparatus 130 as illustrated, and the key member 128 is pressed by the screw member 126 to prevent the sleeve 122 from being unfastened.
A still further conventional roll D shown in FIG. 4 includes a holder 132 fitted on a roll shaft 134, a clamp member 136 fitted on the holder 132 so as to cooperate with it to define a dove-tail groove 138, and a ring 140 fitted in the dove-tail groove 138 and clamped thereto by the clamp member 136. In this roll, the ring 140 is bonded to the holder 132 by an adhesive.
In the rolls A and C, insomuch as there is a clearance between the sleeve and the ring, the pressure exerted between the sleeve and the ring is small in comparison with the pressure exerted between the sleeve and the shaft. As a result, the strength of bonding between the ring and the sleeve is so small that the ring is liable to be shifted due to the torque exerted during the rolling operation. In order to prevent such shifting, the ring has to be made considerably greater in width to obtain a sufficient strength of bonding, so that the roll has the disadvantage that it is high in cost.
Further, in the roll B, since the wear-resistant ring is directly fitted on the shaft, the shaft is susceptible to wear, and hence the strength of bonding of the ring to the shaft is lowered. Besides, insomuch as the inner peripheral surface of the wear-resistant ring has to be processed into a tapered form, the manufacturing cost is increased unduly. Finally, in the roll D, the ring is fixed to the holder only by a bonding force of the adhesive. Accordingly, when the adhesive layer is damaged because of fatigue or the like, the strength of bonding may be suddenly lowered, so that the ring may undergo a slippage which may, in turn, lead to a breakdown.